解析自变量和构建值 ¶

字符串和缓冲 ¶

These formats allow accessing an object as a contiguous chunk of memory. You don’t have to provide raw storage for the returned unicode or bytes area.

In general, when a format sets a pointer to a buffer, the buffer is managed by the corresponding Python object, and the buffer shares the lifetime of this object. You won’t have to release any memory yourself. The only exceptions are es , es# , et and et# .

However, when a Py_buffer structure gets filled, the underlying buffer is locked so that the caller can subsequently use the buffer even inside a Py_BEGIN_ALLOW_THREADS block without the risk of mutable data being resized or destroyed. As a result, you have to call PyBuffer_Release() after you have finished processing the data (or in any early abort case).

除非另有说明，缓冲不以 NULL 结尾。

Some formats require a read-only 像字节对象 , and set a pointer instead of a buffer structure. They work by checking that the object’s PyBufferProcs.bf_releasebuffer field is NULL , which disallows mutable objects such as bytearray .

s ( str ) [const char *]

Convert a Unicode object to a C pointer to a character string. A pointer to an existing string is stored in the character pointer variable whose address you pass. The C string is NUL-terminated. The Python string must not contain embedded null code points; if it does, a ValueError exception is raised. Unicode objects are converted to C strings using 'utf-8' encoding. If this conversion fails, a UnicodeError 被引发。

注意

这种格式不接受 像字节对象 . If you want to accept filesystem paths and convert them to C character strings, it is preferable to use the O& format with PyUnicode_FSConverter() as converter .

3.5 版改变： 先前， TypeError was raised when embedded null code points were encountered in the Python string.

s* ( str or 像字节对象 ) [Py_buffer]

This format accepts Unicode objects as well as bytes-like objects. It fills a Py_buffer structure provided by the caller. In this case the resulting C string may contain embedded NUL bytes. Unicode objects are converted to C strings using 'utf-8' 编码。

s# ( str , read-only 像字节对象 ) [const char *, int or Py_ssize_t ]

像 s* , except that it doesn’t accept mutable objects. The result is stored into two C variables, the first one a pointer to a C string, the second one its length. The string may contain embedded null bytes. Unicode objects are converted to C strings using 'utf-8' 编码。

z ( str or None ) [const char *]

像 s , but the Python object may also be None , in which case the C pointer is set to NULL .

z* ( str , 像字节对象 or None ) [Py_buffer]

像 s* , but the Python object may also be None , in which case the buf member of the Py_buffer structure is set to NULL .

z# ( str , read-only 像字节对象 or None ) [const char *, int]

像 s# , but the Python object may also be None , in which case the C pointer is set to NULL .

y (read-only 像字节对象 ) [const char *]

This format converts a bytes-like object to a C pointer to a character string; it does not accept Unicode objects. The bytes buffer must not contain embedded null bytes; if it does, a ValueError 异常被引发。

3.5 版改变： 先前， TypeError was raised when embedded null bytes were encountered in the bytes buffer.

y* ( 像字节对象 ) [Py_buffer]

This variant on s* doesn’t accept Unicode objects, only bytes-like objects. This is the recommended way to accept binary data.

y# (read-only 像字节对象 ) [const char *, int]

This variant on s# doesn’t accept Unicode objects, only bytes-like objects.

S ( bytes ) [PyBytesObject *]

Requires that the Python object is a bytes object, without attempting any conversion. Raises TypeError if the object is not a bytes object. The C variable may also be declared as PyObject* .

Y ( bytearray ) [PyByteArrayObject *]

Requires that the Python object is a bytearray object, without attempting any conversion. Raises TypeError if the object is not a bytearray object. The C variable may also be declared as PyObject* .

u ( str ) [Py_UNICODE *]

Convert a Python Unicode object to a C pointer to a NUL-terminated buffer of Unicode characters. You must pass the address of a Py_UNICODE pointer variable, which will be filled with the pointer to an existing Unicode buffer. Please note that the width of a Py_UNICODE character depends on compilation options (it is either 16 or 32 bits). The Python string must not contain embedded null code points; if it does, a ValueError 异常被引发。

3.5 版改变： 先前， TypeError was raised when embedded null code points were encountered in the Python string.

Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Py_UNICODE API；请迁移到使用 PyUnicode_AsWideCharString() .

u# ( str ) [Py_UNICODE *, int]

This variant on u stores into two C variables, the first one a pointer to a Unicode data buffer, the second one its length. This variant allows null code points.

Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Py_UNICODE API；请迁移到使用 PyUnicode_AsWideCharString() .

Z ( str or None ) [Py_UNICODE *]

像 u , but the Python object may also be None , in which case the Py_UNICODE pointer is set to NULL .

Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Py_UNICODE API；请迁移到使用 PyUnicode_AsWideCharString() .

Z# ( str or None ) [Py_UNICODE *, int]

像 u# , but the Python object may also be None , in which case the Py_UNICODE pointer is set to NULL .

Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Py_UNICODE API；请迁移到使用 PyUnicode_AsWideCharString() .

U ( str ) [PyObject *]

Requires that the Python object is a Unicode object, without attempting any conversion. Raises TypeError if the object is not a Unicode object. The C variable may also be declared as PyObject* .

w* (read-write 像字节对象 ) [Py_buffer]

This format accepts any object which implements the read-write buffer interface. It fills a Py_buffer structure provided by the caller. The buffer may contain embedded null bytes. The caller have to call PyBuffer_Release() when it is done with the buffer.

es ( str ) [const char *encoding, char **buffer]

This variant on s is used for encoding Unicode into a character buffer. It only works for encoded data without embedded NUL bytes.

This format requires two arguments. The first is only used as input, and must be a const char* which points to the name of an encoding as a NUL-terminated string, or NULL , in which case 'utf-8' encoding is used. An exception is raised if the named encoding is not known to Python. The second argument must be a char** ; the value of the pointer it references will be set to a buffer with the contents of the argument text. The text will be encoded in the encoding specified by the first argument.

PyArg_ParseTuple() will allocate a buffer of the needed size, copy the encoded data into this buffer and adjust *buffer to reference the newly allocated storage. The caller is responsible for calling PyMem_Free() to free the allocated buffer after use.

et ( str , bytes or bytearray ) [const char *encoding, char **buffer]

如同 es except that byte string objects are passed through without recoding them. Instead, the implementation assumes that the byte string object uses the encoding passed in as parameter.

es# ( str ) [const char *encoding, char **buffer, int *buffer_length]

This variant on s# is used for encoding Unicode into a character buffer. Unlike the es format, this variant allows input data which contains NUL characters.

It requires three arguments. The first is only used as input, and must be a const char* which points to the name of an encoding as a NUL-terminated string, or NULL , in which case 'utf-8' encoding is used. An exception is raised if the named encoding is not known to Python. The second argument must be a char** ; the value of the pointer it references will be set to a buffer with the contents of the argument text. The text will be encoded in the encoding specified by the first argument. The third argument must be a pointer to an integer; the referenced integer will be set to the number of bytes in the output buffer.

There are two modes of operation:

若 *buffer points a NULL pointer, the function will allocate a buffer of the needed size, copy the encoded data into this buffer and set *buffer to reference the newly allocated storage. The caller is responsible for calling PyMem_Free() to free the allocated buffer after usage.

若 *buffer points to a non- NULL pointer (an already allocated buffer), PyArg_ParseTuple() will use this location as the buffer and interpret the initial value of *buffer_length as the buffer size. It will then copy the encoded data into the buffer and NUL-terminate it. If the buffer is not large enough, a ValueError will be set.

In both cases, *buffer_length is set to the length of the encoded data without the trailing NUL byte.

et# ( str , bytes or bytearray ) [const char *encoding, char **buffer, int *buffer_length]

如同 es# except that byte string objects are passed through without recoding them. Instead, the implementation assumes that the byte string object uses the encoding passed in as parameter.

数字 ¶

b ( int ) [unsigned char]

Convert a nonnegative Python integer to an unsigned tiny int, stored in a C unsigned char .

B ( int ) [unsigned char]

Convert a Python integer to a tiny int without overflow checking, stored in a C unsigned char .

h ( int ) [short int]

将 Python 整数转换为 C short int .

H ( int ) [unsigned short int]

将 Python 整数转换为 C unsigned short int ，没有溢出校验。

i ( int ) [int]

将 Python 整数转换为纯 C int .

I ( int ) [unsigned int]

将 Python 整数转换为 C unsigned int ，没有溢出校验。

l ( int ) [long int]

将 Python 整数转换为 C long int .

k ( int ) [unsigned long]

将 Python 整数转换为 C unsigned long 没有溢出校验。

L ( int ) [long long]

将 Python 整数转换为 C long long .

K ( int ) [unsigned long long]

将 Python 整数转换为 C unsigned long long 没有溢出校验。

n ( int ) [Py_ssize_t]

将 Python 整数转换为 C Py_ssize_t .

c ( bytes or bytearray of length 1) [char]

Convert a Python byte, represented as a bytes or bytearray object of length 1, to a C char .

3.3 版改变： Allow bytearray 对象。

C ( str of length 1) [int]

Convert a Python character, represented as a str object of length 1, to a C int .

f ( float ) [float]

将 Python 浮点数转换为 C float .

d ( float ) [double]

将 Python 浮点数转换为 C double .

D ( complex ) [Py_complex]

将 Python 复数转换为 C Py_complex 结构。

其它对象 ¶

O (object) [PyObject *]

将 Python 对象 (无需任何转换) 存储在 C 对象指针中。因此，C 程序接收实际传递对象。不会递增对象的引用计数。存储指针不是 NULL .

O! (object) [ typeobject , PyObject *]

Store a Python object in a C object pointer. This is similar to O , but takes two C arguments: the first is the address of a Python type object, the second is the address of the C variable (of type PyObject* ) into which the object pointer is stored. If the Python object does not have the required type, TypeError 被引发。

O& (object) [ converter , anything ]

Convert a Python object to a C variable through a converter function. This takes two arguments: the first is a function, the second is the address of a C variable (of arbitrary type), converted to void * 。 converter function in turn is called as follows:

status = converter(object, address);
											

where object is the Python object to be converted and address 是 void* argument that was passed to the PyArg_Parse*() function. The returned status 应该为 1 for a successful conversion and 0 if the conversion has failed. When the conversion fails, the converter function should raise an exception and leave the content of address unmodified.

若 converter 返回 Py_CLEANUP_SUPPORTED , it may get called a second time if the argument parsing eventually fails, giving the converter a chance to release any memory that it had already allocated. In this second call, the object parameter will be NULL; address will have the same value as in the original call.

3.1 版改变： Py_CLEANUP_SUPPORTED 被添加。

p ( bool ) [int]

Tests the value passed in for truth (a boolean p redicate) and converts the result to its equivalent C true/false integer value. Sets the int to 1 if the expression was true and 0 if it was false. This accepts any valid Python value. See 真值测试 for more information about how Python tests values for truth.

3.3 版新增。

(items) ( tuple ) [ matching-items ]

The object must be a Python sequence whose length is the number of format units in items . The C arguments must correspond to the individual format units in items . Format units for sequences may be nested.

It is possible to pass “long” integers (integers whose value exceeds the platform’s LONG_MAX ) however no proper range checking is done — the most significant bits are silently truncated when the receiving field is too small to receive the value (actually, the semantics are inherited from downcasts in C — your mileage may vary).

A few other characters have a meaning in a format string. These may not occur inside nested parentheses. They are:

|

Indicates that the remaining arguments in the Python argument list are optional. The C variables corresponding to optional arguments should be initialized to their default value — when an optional argument is not specified, PyArg_ParseTuple() does not touch the contents of the corresponding C variable(s).

$

PyArg_ParseTupleAndKeywords() only: Indicates that the remaining arguments in the Python argument list are keyword-only. Currently, all keyword-only arguments must also be optional arguments, so | must always be specified before $ in the format string.

3.3 版新增。

:

The list of format units ends here; the string after the colon is used as the function name in error messages (the “associated value” of the exception that PyArg_ParseTuple() raises).

;

The list of format units ends here; the string after the semicolon is used as the error message instead of the default error message. : and ; mutually exclude each other.

Note that any Python object references which are provided to the caller are borrowed references; do not decrement their reference count!

Additional arguments passed to these functions must be addresses of variables whose type is determined by the format string; these are used to store values from the input tuple. There are a few cases, as described in the list of format units above, where these parameters are used as input values; they should match what is specified for the corresponding format unit in that case.

For the conversion to succeed, the arg object must match the format and the format must be exhausted. On success, the PyArg_Parse*() functions return true, otherwise they return false and raise an appropriate exception. When the PyArg_Parse*() functions fail due to conversion failure in one of the format units, the variables at the addresses corresponding to that and the following format units are left untouched.

API 函数 ¶

int PyArg_ParseTuple ( PyObject  *args , const char  *format , ... ) ¶

仅将函数的位置参数，剖析成局部变量。返回 True 当成功时；当故障时，它返回 False 并引发适当异常。

int PyArg_VaParse ( PyObject  *args , const char  *format , va_list  vargs ) ¶

等同于 PyArg_ParseTuple() ，除了它接受 va_list 而不是可变数自变量。

int PyArg_ParseTupleAndKeywords ( PyObject  *args , PyObject  *kw , const char  *format , char  *keywords[] , ... ) ¶

将函数的位置和关键词参数两者，剖析成局部变量。 keywords 自变量是 NULL 结尾的关键词参数名称的数组。空名称表示 仅位置参数 。返回 true 当成功时；当故障时，它返回 False 并引发适当异常。

3.6 版改变： 添加支持 仅位置参数 .

int PyArg_VaParseTupleAndKeywords ( PyObject  *args , PyObject  *kw , const char  *format , char  *keywords[] , va_list  vargs ) ¶

等同于 PyArg_ParseTupleAndKeywords() ，除了它接受 va_list 而不是可变数自变量。

int PyArg_ValidateKeywordArguments ( PyObject  * ) ¶

确保关键词自变量字典中的键是字符串。这才需要若 PyArg_ParseTupleAndKeywords() 未使用，因为后者已做此校验。

3.2 版新增。

int PyArg_Parse ( PyObject  *args , const char  *format , ... ) ¶

Function used to deconstruct the argument lists of “old-style” functions — these are functions which use the METH_OLDARGS parameter parsing method, which has been removed in Python 3. This is not recommended for use in parameter parsing in new code, and most code in the standard interpreter has been modified to no longer use this for that purpose. It does remain a convenient way to decompose other tuples, however, and may continue to be used for that purpose.

int PyArg_UnpackTuple ( PyObject  *args , const char  *name , Py_ssize_t  min , Py_ssize_t  max , ... ) ¶

A simpler form of parameter retrieval which does not use a format string to specify the types of the arguments. Functions which use this method to retrieve their parameters should be declared as METH_VARARGS in function or method tables. The tuple containing the actual parameters should be passed as args ; it must actually be a tuple. The length of the tuple must be at least min and no more than max ; min and max may be equal. Additional arguments must be passed to the function, each of which should be a pointer to a PyObject* variable; these will be filled in with the values from args ; they will contain borrowed references. The variables which correspond to optional parameters not given by args will not be filled in; these should be initialized by the caller. This function returns true on success and false if args is not a tuple or contains the wrong number of elements; an exception will be set if there was a failure.

This is an example of the use of this function, taken from the sources for the _weakref helper module for weak references:

static PyObject *
weakref_ref(PyObject *self, PyObject *args)
{
    PyObject *object;
    PyObject *callback = NULL;
    PyObject *result = NULL;
    if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) {
        result = PyWeakref_NewRef(object, callback);
    }
    return result;
}
											

调用 PyArg_UnpackTuple() in this example is entirely equivalent to this call to PyArg_ParseTuple() :

PyArg_ParseTuple(args, "O|O:ref", &object, &callback)